1. Field of the Invention
This invention relates to a method of forming a forgery-preventive image and an apparatus therefor which are capable of forming a forgery-preventive image on a print medium, such as a card, by using printing technology.
2. Prior Art
In a conventional method of forming a forgery-preventive image, a print medium formed of two (or more) image-receiving layers is used for printing. In the method, after printing on a first layer of the two image-receiving layers, a transparent second layer is affixed onto the first layer, and then printing is performed on the second layer. In this case, images partially different from each other are printed on the respective first and second layers, such that the two images form an entire image in a synthesized manner when they are viewed from the front of the print medium. Further, determination as to whether forgery has been committed is made by cutting the print medium printed with the images and inspecting a cross section of the print medium to determine whether or not the entire image is formed as a multi-layered image.
In the method, however, e.g. when a card is used as a print medium, it is required to carry out complicated and troublesome operations of alignment or positioning of the two images and corresponding edges of the two layers of the card during lamination of image-receiving layers after printing, and hence it takes a lot of time and labor to make the card as a medium printed with a forgery-preventive image, which results in an increase in manufacturing costs.
It is an object of the invention to provide a method of forming a forgery-preventive image and an apparatus therefor which are capable of easily making a forgery-preventive medium without spoiling ease of determination as to whether forgery has been committed.
To attain the above object, according to a first aspect of the invention, there is provided a method of forming a forgery-preventive image, comprising the steps of:
printing an image on an ink image-receiving sheet by using a sublimable dye ink, thereby causing the sublimable dye ink to be held by the ink image-receiving sheet;
heating the image-receiving sheet and a medium body overlaid upon each other, thereby causing diffusion of the sublimable dye ink held in the ink image-receiving sheet in a surface of the medium body and color development, and
controlling an amount of heat applied to the ink image-receiving sheet and the medium body so as to adjust depth of diffusion of the sublimable dye ink.
To attain the above object, according to a second aspect of the invention, there is provided an apparatus for forming a forgery-preventive image, comprising:
printing means for printing an image on an ink image-receiving sheet by using a sublimable dye ink, thereby causing the sublimable dye ink to be held by the ink image-receiving sheet;
heating means for heating the image-receiving sheet and a medium body overlaid upon each other, thereby causing diffusion of the sublimable dye ink held in the ink image-receiving sheet in a surface of the medium body and color development, and
heat amount control means for controlling an amount of heat applied to the ink image-receiving sheet and the medium body so as to adjust depth of diffusion of the sublimable dye ink.
According to the method of forming a forgery-preventive image and the apparatus therefor, when an image is printed on the print medium, the sublimable dye ink is impregnated into the ink image-receiving sheet and held therein. Then, the print medium is heated in this state, and this causes diffusion of the sublimable dye ink from the ink image-receiving sheet into the surface layer (surface) of the medium body and color development to form an image.
In general, it is observed that when an image (sublimable dye ink) is transferred from the ink image-receiving sheet to the medium body, the diffusion (transfer) depth of the sublimable dye ink varies with the length of heating time, or more accurately, the amount of heat. That is, the sublimable dye ink penetrates into a deeper location to be fixed thereat as the amount of heat applied thereto increases. Therefore, fixation depth of the sublimable dye ink in the surface layer of the medium body can be kept concealed by finding out the correlation between the amount of heat applied to the print medium and diffusion depth of the sublimable dye ink in the medium body and controlling the amount of heat applied to the print medium. Further, by inspecting a cross section of the medium body, it is possible to easily determine whether or not the medium body is a forgery.
Preferably, the method further includes the step of dividing data of the image into data of a plurality of divisional images, and the step of separating the ink image-receiving sheet and the medium body which have been heated, from each other, and the step of printing includes printing one of the plurality of divisional images on a new ink image-receiving sheet, and wherein a cycle of the step of printing, the step of heating, and the step of separating is repeated a number of times corresponding to the number of the plurality of divisional images, and wherein the step of controlling the amount of heat includes progressively reducing the amount of heat as the cycle is repeated.
Preferably, the apparatus further includes image dividing means for dividing data of the image into data of a plurality of divisional images, and separation means for separating the ink image-receiving sheet and the medium body which have been heated, from each other, and control means for controlling operations of the printing means, the heating means, the separation means, and the heat amount control means, based on the data of the plurality of divisional images formed by the image dividing means, and wherein printing means prints one of the plurality of divisional images on a new ink image-receiving sheet, and the control means carries out control such that a cycle of printing on the ink image-receiving sheet by the printing means, heating of the ink image-receiving sheet and the medium body overlaid upon each other by the heating means, and separation of the ink image-receiving sheet and the medium body overlaid upon each other from each other by the separation means is repeated a number of times corresponding to the number of the plurality of divisional images and that the amount of heat is progressively reduced by the heat amount control means as the cycle is repeated.
According to these preferred embodiments, an image is divided into a plurality of divisional images, and printing and heating are repeatedly carried out on a divisional image-by-divisional image basis to form a desired entire image. Further, in the processes of the repeated heating operations, the amount of heat applied to the print medium is progressively reduced. Accordingly, a divisional images formed earlier is fixed at a deeper location in the surface layer of the medium body, whereas a divisional image formed later is fixed at a shallower location. Therefore, fixation depth of sublimable dye ink of each divisional image in the surface layer of the medium body can be kept concealed. Further, by determining the fixation depth of each sublimable dye ink of each divisional image through inspection of a cross section of the medium body, it is possible to easily determine whether or not the medium body is a forgery.
More preferably, the method further includes the step of overlaying the ink image-receiving sheet on the medium body, prior to the step of printing, and the cycle includes the step of overlaying.
More preferably, the apparatus further includes ink image-receiving sheet supply means for supplying a new ink image-receiving sheet, and overlay means for overlaying the ink image-receiving sheet and the print medium upon one another, and the cycle includes supplying of the ink image-receiving sheet by the ink image-receiving sheet supply means, and overlaying of the ink image-receiving sheet and the print medium upon one another by the overlay means.
Further preferably, the overlay means overlays the ink image-receiving sheet and the medium body upon each other prior to printing by the printing means.
More preferably, the ink image-receiving sheet is formed such that the ink image-receiving sheet can be affixed to the medium body, and the step of overlaying includes affixing the ink image-receiving sheet to the medium body.
According to this preferred embodiment, it is not only easy to deal with the print medium, but also possible to transfer the sublimable dye ink stably from the ink image-receiving sheet to the medium body. Particularly, it is possible to use heating means of non-contact type.
Preferably, the method includes the step of overlaying the ink image-receiving sheet on the medium body, which is carried out posterior to the step of printing and simultaneously with the step of heating, and wherein the cycle includes the step of overlaying which is carried out simultaneously with the step of heating.
Similarly, the overlay means is formed integrally with the heating means, and overlays the ink image-receiving sheet and the medium body upon each other posterior to printing of the divisional ink by the printing means and simultaneously with heating by the heating means.
More preferably, the step of dividing the data of the image includes dividing the data of the image into data of a plurality of divisional images having respective different colors.
More preferable, the image dividing means divides the data of the image into data of a plurality of divisional images having respective different colors.
According to these preferred embodiments, data of the image is divided into data of a plurality of divisional images having respective different colors (color division; more accurately, color decomposition) and then printing and heating are repeatedly carried out on a divisional image-by-divisional image basis to form a desired entire image. In the repeated heating operation, the amount of heat applied to the print medium is progressively reduced. Accordingly, a divisional image formed earlier is fixed at a deeper location in the surface layer of the medium body, whereas a divisional image formed later is fixed at a shallower location. Therefore, fixation depth of sublimable dye ink of each color in the surface layer of the medium body can be kept concealed. Further, by determining the fixation depth and color of each sublimable dye ink through inspection of a cross section of the medium body, it is possible to easily determine whether or not the medium body is a forgery.
Further preferably, the number of the plurality of divisional images is two, and the method further includes the step of setting one of the two divisional images to be formed when the cycle is executed first to one having a darker color, and another of the two divisional images to be formed when the cycle is executed next to one having a lighter color.
According to this preferred embodiment, the divisional image having a darker color is fixed at a deeper location in the surface layer of the medium body, while the divisional image having a brighter color is fixed at a shallower location in the same. Therefore, by checking the brightness and darkness of the colors of a cross section of the medium body, it is also possible to easily determine whether or not the medium body is a forgery.
More preferably, the step of dividing the data of the image includes dividing the data of the image into data of a plurality of divisional images representative of respective different image elements.
More preferably, the image dividing means divides the data of the image into data of a plurality of divisional images representative of respective different image elements.
According to these preferred embodiments, the data of the image is divided into data of a plurality of divisional images representing of respective image elements, and then printing and heating are carried out on a divisional image-by-divisional image basis to form a desired entire image. In the repeated heating operations, the amount of heat applied to the print medium is progressively reduced. Accordingly, a divisional image formed earlier is fixed at a deeper location in the surface layer of the medium body, whereas a divisional image formed later is fixed at a shallower location. Therefore, fixation depth of sublimable dye ink of each divisional image in the surface layer of the medium body can be kept concealed. Further, by checking the fixation depth and presence or absence of each divisional image through inspection of a specific cross section of the medium body, it is possible to easily determine whether or not the medium body is a forgery.
Further preferably, the number of the plurality of divisional images is two, and one of the two divisional images to be formed when the cycle is executed first, and another of the two divisional images to be formed when the cycle is executed next are caused to partially overlap each other.
According to this preferred embodiment, the divisional pattern of the image is complicated, and hence it is possible to make forgery very difficult, without spoiling ease of determination as to whether forgery has been committed.
More preferably, the step of dividing the data of the image includes dividing the data of the image into data of a plurality of divisional images having respective different densities.
More preferably, the image dividing means divides the data of the image into data of a plurality of divisional images having respective different densities.
According to these preferred embodiments, the data of an image is divided into data of a plurality of divisional images having respective different densities, and then printing and heating are repeatedly carried out on a divisional image-by-divisional image basis to form a desired entire image. In the repeated heating operations, the amount of heat applied to the print medium is progressively reduced. Accordingly, a divisional image formed earlier is fixed at a deeper location in the surface layer of the medium body, whereas a divisional image formed later is fixed at a shallower location. Therefore, fixation depth of sublimable dye ink of each density in the surface layer of the medium body can be kept concealed. Further, by checking the fixation depth and density of each sublimable dye ink through inspection of a cross section of the medium body, it is possible to easily determine whether or not the medium body is a forgery.
Preferably, the number of the plurality of divisional images is two, and the method further includes the step of setting one of the two divisional images to be formed when the cycle is executed first to one having a higher density, and another of the two divisional images to be formed when the cycle is executed next to one having a lower density.
According to this preferred embodiment, a divisional image having the higher density is fixed at a deeper location in the surface layer of the medium body, while a density-divisional image having the lower density is fixed at a shallower location in the same. The difference in density between the two divisional images having respective different densities is particularly conspicuous, so that by inspecting a cross section of the medium body, it is even easier to determine as to whether or not the medium body is a forgery.
More preferably, the medium body includes a white layer forming a substrate layer and permitting ink fixation, and a transparent layer laminated on a surface of the white layer and permitting ink fixation, and the number of the plurality of divisional images is two, the sublimable dye ink being heated and fixed in a surface layer of the white layer when the cycle is executed first, while the sublimable dye ink being heated and fixed in the transparent layer when the cycle is executed next.
According to this preferred embodiment, simply by checking whether each of the divisional images is fixed in the white layer or in the transparent layer, it is possible to determine very easily whether or not the medium body is a forgery,
Further, preferably, the medium body has a fluorine film layer laminated on an outermost surface layer thereof on which the ink image-receiving sheet is to be overlaid.
According to this preferred embodiment, when the ink image-receiving sheet is heated, the sublimable dye ink held in the ink image-receiving sheet passes through the fluorine film layer, followed by being diffused and fixed in the surface layer of the medium body. As a result, after the ink image-receiving sheet is removed, the fluorine film layer functions as a protective layer (laminating layer) for protecting the image fixed in the surface layer of the medium body. The fluorine film layer is not only weather-resistant, light-resistant, heat-resistant, rub or abrasion-resistant and chemical-resistant, but also glossy, so that it is possible to make an excellent media body.
Preferably, the medium body is a card.
According to this preferred embodiment, a card having forgery preventive function can be produced easily at low costs.
Preferably, the step of printing includes printing by an ink jet printing method.
Preferably, the printing means carries out printing by an ink jet printing method.
According to these preferred embodiments, it is possible to carry out printing easily without any contact with the ink image-receiving sheet and form a clear image. Further, a color image, in particular, can be formed easily and speedily.
Preferably, the step of heating includes causing the print medium to pass by a heat source which is being driven for heating, at a constant speed, and the step of controlling the amount of heat includes controlling at least one of a temperature of the heat source and a speed of the print medium.
Preferably, the heating means includes a heat source, and a media feed mechanism for causing the print medium to pass by the heat source which is being driven for heating, at a constant speed, and the heat amount control means controls the amount of heat by controlling at least one of a temperature of the heat source and a speed of the print medium fed by the media feed mechanism.
According to these preferred embodiments, the control of the amount of heat applied to the print medium is carried out by controlling at least one of the temperature of the heat source and the speed of the print medium. Therefore, it is possible to carry out the control of the heat amount by selectively using the two control elements, which facilitates the control and makes it possible to heat the whole print medium uniformly.
The above and other objects, features, and advantages of the invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings.